The Americans with Disabilities Act passed into law assuring all people an equal opportunity to gain access to all buildings used by the general public. Even with the adoption of this law, non-ambulatory people are generally afforded ingress to all buildings but not necessarily given a protected means of egress from the building during emergency circumstances. During a building emergency, such as a fire, ambulatory and non-ambulatory building occupants, even those who are clear thinking people under normal circumstances, can panic or make irrational decisions, which can result in injury to themselves and others.
Faced with a difficult emergency situation, people many times revert to their most comfortable behavior. In terms of leaving a multi-story building during nonemergency conditions, this means using the elevator. People normally arrive at and depart from the upper floors of the building via the elevator, and most never have used the emergency stair system. Given a typical response to an emergency situation, people will retrace their most familiar path of travel, which usually includes passing in front of the elevators as they attempt to find an escape route from the building.
During an emergency situation, elevators are usually taken out of service except for controlled use by the fire department. Accordingly, the building occupants cannot currently use the elevator as a safe and reliable means of egress during the emergency situation, such as a fire. They must therefore attempt either to use an unfamiliar stairway or wait within the building to be rescued. Non-ambulatory and disabled people unable to use stairs have no choice but to await help.
In multiple level buildings it is difficult to evacuate building occupants via the stairs. Generally, there are two classifications of buildings relative to fire and life safety: high-rise buildings and mid-rise buildings. The major distinction is that a standard hook and ladder type fire apparatus can only reach the point of a building about 75 feet or 6 floors above the ground, so "high-rise" buildings, those above about 6 floors, must be evacuated from within the building.
In mid-rise buildings, fire departments use the stairs to transport personnel and equipment to the fire floor, which drastically interferes with the designed egress capacity of the exit stair system. In high-rise buildings, the difficulties with occupant evacuation are compounded. Although the elevator cars can be used by the fire department to transport personnel to a selected staging floor below the fire floor, many times smoke is present in the hoistway shaft by the time of their arrival to the staging floor. Stack effect pressures within the building move large volumes of air through the vertical hoistway shafts. The shafts quickly become smoke filled chimneys and are often capable of transporting smoke throughout the building in a matter of minutes.
Since the fire department cannot reach the building's upper floors from outside the building, the building's occupants are forced to either use an exit stairway to evacuate or remain in the burning building until rescued by the fire department. As the fire department personnel uses one stairway to advance on the fire, the stairway doors are typically propped open with fire hoses, thereby allowing smoke from the fire floor to enter the stairway. Accordingly, that stairway is not suitable for evacuation of the building occupants during an emergency.
The evacuation of people is the primary responsibility of the fire department. The fire department personnel do not begin a fire attack until the building occupants are safe. Conventional evacuation of building occupants, however, is a very time consuming process. During a fire, the chaotic environment increases the complexity and danger of an evacuation procedure, which also usually increases the time required to evacuate the building. It is even more difficult and time consuming to evacuate the non-ambulatory, injured, and disabled occupants.
Even if available for use, conventional elevator systems are an unreliable method of escaping a building fire, and under current regulations, can only be used by the fire department under a narrow range of conditions. For example, the elevator system is not used when there is a high risk of a power outage, because such a power outage will shut the elevator system down and potentially trap passengers between floors. The conventional elevator control system is also easily short circuited by water that enters either the machine room or the hoistway shaft. Smoke is easily drawn into the hoistway shaft by naturally occurring stack effect pressures, and the smoke can quickly fill the hoistway, thereby creating an unsafe environment for people without self-contained breathing devices.
Therefore, the elevators are not usable for building occupants as a reliable means of egress during a building fire. Placards stating "Do not use Elevators during a Fire" are commonly placed next to the hall call stations to notify the occupants of the proper emergency exiting strategy. Ambulatory occupants are therefore forced to use exit stairways to escape a building fire, even from the top floors of mega high-rise buildings.
Conventional Emergency Evacuation Procedures
When an emergency condition is identified in a building an alarm signal is manually or automatically provided to the fire department. Upon receiving the alarm signal, the fire department only knows that an alarm has been activated, but it does not know the status of the building systems until the response team arrives at the building and access the building's fire alarm panel or other data information bank. As a result, the response team loses valuable time with respect to controlling the building conditions and establishing a desired building evacuation sequence and emergency response strategy for the particular building.
Even though the fire department response time to arrive at the building is typically less than six or seven minutes, fifteen minutes can easily pass before an evacuation sequence is initiated. The total evacuation time for upper floors of a high-rise building may take up to an hour. During a building fire, time is critical and unnecessary delays can increase the danger of the situation.
In accordance with a typical standard incident command procedure, an incident command post is established in the main floor lobby upon arrival by the fire department. The fire department personnel can then override the elevator system and use the elevators to send an investigation team to a safe point several floors below the fire floor. The investigation team then takes the stairs to the fire floor to assess the extent of the fire involvement and determine the necessary evacuation procedures. Fire Department personnel and equipment are then typically staged two floors below the fire floor and a rescue assistance area is established four floors below the fire floor. Building occupants are then initially evacuated through the stairway to the rescue assistance area.
Conventional Elevator and Fire/Smoke Detection Systems
The basic configuration and operation of an elevator system is well known. A multiple floor building contains a vertical elevator shaft defined by a top, bottom and vertical structural walls through which an elevator car travels between floors. An opening in one of the structural walls at each floor forms a hoistway entrance through which building occupants can safely pass into and out of the elevator car when the elevator car is adjacent to the hoistway entrance during non-emergency conditions. An interlock mechanism connects the elevator car door to the hoistway door when the elevator car is adjacent to the hoistway entrance and the elevator car door opened or closed.
The elevator car's vertical travel in the hoistway is controlled by a conventional elevator control system. The elevator control system typically includes a motion controller and a car controller that receives signals from hall call stations located on each floor. The elevator control system is adapted to position the car adjacent the signaling floor to allow passengers to enter or exit the car. When a "send" or "floor destination" button within the car is activated, a signal is sent to the elevator control system, which in turn moves the car to the designated floor and opens the door to allow passengers to exit the car. Accordingly, the elevator control system permits the building occupants to quickly and efficiently travel between floors of the multi level building during normal conditions.
The typical high-rise building has a fire alarm/smoke detection system, such as a system manufactured by the Simplex Corporation. The fire alarm/smoke detection system is comprised of a plurality of smoke and heat sensing devices which are remotely located throughout the building and capable of detecting the early signs of a building fire. These remote detectors are electrically connected to a central fire alarm panel and are functional to either open or close a series of relay contacts, thereby capable of sending a signal to a building security station, to the fire department, and to an alarm system that alerts the building occupants with audible and strobe alarms. The central fire alarm panel also initiates the operation of fire doors, air conditioning systems, and the like within the building. Many times the fire alarm/smoke detection system also has an auxiliary relay contact as a backup system that is functionally connected to the elevator control system. The elevator control system is programmed, such that when it receives a distinctive signal from the central fire alarm panel, the elevator control system recalls all elevator cars to a predesignated floor, e.g., the lobby floor, and prevents elevator cars from stopping at a floor where smoke has been detected.
Prior to 1973, elevators remained fully operational during a building fire without any safeguards that took into account the location of the building fire. Building occupants on the fire floor trying to quickly escape a fire could push the elevator hall call station buttons and inadvertently call an elevator full of people to the fire floor. Building security personnel investigating a signaling smoke detector could likewise find themselves faced with the fire as the elevator doors opened on the fire floor. Fire temperatures or water flowing from the activation of a fire sprinkler could also short circuit the elevator hall call station buttons and call the elevators to the fire floor, thereby jeopardizing fire department personnel trying to utilize the elevators to stage personnel and equipment.
In an effort to minimize this dangerous situation, all modem elevator systems are equipped with a recall function that is initiated either automatically by the detection of smoke or manually by building security or fire department personnel. The 1996 Edition of the ASME A17.1 code for elevators requires recall on all elevators. Once sent into alarm condition, all hall call stations are de-energized and all elevator cars are automatically recalled to a predesignated floor of the building. If the predesignated floor is the floor where smoke has been detected, the elevator cars are recalled to an alternate floor. The elevators are parked with the doors open and the elevators are temporarily taken out of service. Upon arrival, the fire department can override the recall function by activating a fire department key switch to utilize each elevator car individually. The conventional elevators, however, in an emergency such as a building fire, cannot be used as a safe means of egress of occupants from the building even under the control of the fire department.
Many state of the art buildings are also equipped with a smoke detection system that is designed and installed in accordance with industry standards. At least one smoke detector is located in each elevator lobby and is functionally connected to the elevator control system. Additional remote smoke detectors may be located throughout the building and are functionally connected to the elevator control system. When smoke from a building fire is detected by the elevator lobby detector or by a remote smoke detector, an alarm signal activates building emergency systems, which results in the closing of certain predetermined doors, sounding audible alarms, and the like. The elevator recall function is activated either automatically or manually, and the elevator control system deactivates the hall call stations and the car destination buttons.
If an elevator car is moving upwardly, the elevator control system deenergizes the motion controller, stops the car's ascent, and activates the motion controller to position the car at a predesignated egress floor. If the car is moving downwardly, the elevator control system activates the motion controller to continue the decent to the predesignated egress floor.
Four basic elements are important for an elevator car to be used as an emergency means of egress, which are not all provided by conventional elevator systems: reliable power, a smoke free hoistway shaft, no unshielded electronics in the hoistway or machine room that can be damaged by water, and the ability of the elevator system to respond to changing building conditions due to migrating smoke. Power outages can stall the elevator car, trapping passengers within the hoistway shaft and further consuming fire department resources to locate the stalled car and evacuate the trapped passengers. An emergency power source is only a mandatory building code requirement in buildings above 75 feet to the highest occupied level. Accordingly, there is a need for an elevator system that is usable for emergency evacuation of building occupants during a building fire or other emergency.
One significant reason that conventional elevator systems are not used for emergency egress during a building fire is the danger presented by smoke. Smoke that is present at the hoistway door can also be interpreted by the electronic eye as an obstacle in the elevator doorway, thereby preventing the door from closing properly. Smoke also contains toxic gases and products of combustion that create an untenable environment for people, even at room temperature. Smoke in the elevator hoistway would subject any passengers riding in the elevator car to such an untenable environment and expose them to increased risk.
At least one model building code in the United States prescribes an enclosed elevator lobby in all buildings to separate the hoistway shaft from the remainder of the building in an effort to control smoke. Some building code jurisdictions allow an air pressurization system utilizing the elevator hoistway shaft to create positive air flow from the shaft into the fire floor to blow smoke out of and away from the hoistway shaft. An automatically deployable hoistway door gasketing system is described in U.S. Pat. Nos. 5,195,594 and 5,383,510 to keep smoke from entering the hoistway. Additional methods of providing a smoke barrier at the hoistway door are described in my co-pending U.S. applications, namely, U.S. patent application Ser. No. 08/732,129, filed Oct. 18, 1996, and U.S. patent application Ser. No. 08/423,958, filed Apr. 18, 1995, each of which is incorporated herein by reference in their entireties.
Another reason for not using the elevator system for egress during an emergency is the risks presented when water gets into the elevator system. Water used for fire suppression, such as from automatic fire sprinklers or from the fire department hoses, is usually present during a building fire. Water can enter the hoistway and short circuit the car controls located on the top of the elevator car. A raised sill at the hoistway door or a slight slope of the lobby floor away from the hoistway door can help prevent water from draining into the hoistway shaft. Water entering the hoistway shaft can also be controlled by the water shield/drainage system for the hoistway door, described in my co-pending U.S. patent application Ser. No. 08/751,306, filed Nov. 18, 1996, which is incorporated herein by reference in its entirety.
The evacuation time as calculated in the "Routine Analysis of the People Movement Time for Elevator Evacuation" is about forty minutes for an eleven story building using a single elevator. A twenty-one story building was estimated to take three hours to evacuate. Interviews of building occupants after actual fire incidents indicate the initiation time from first hearing an alarm to beginning any evacuation sequence may exceed thirty minutes. Therefore, the use of the conventional elevator systems for evacuation is neither efficient nor realistic in its present configuration.